A fluorinated compound exhibits high lubricity, water/oil repellency, etc. and thus is suitably used for a surface treatment agent. When water/oil repellency is imparted to the surface of a substrate by such a surface treatment agent, it will be easy to wipe off stain from the surface of the substrate, whereby removability of stain will be improved. Among such fluorinated compounds, a fluorinated ether compound having a poly(oxyperfluoroalkylene) chain with an ether bond (—O—) present at middle in a perfluoroalkyl chain, is particularly excellent in removability of stain of e.g. oils or fats.
A surface treatment agent containing the fluorinated ether compound is used in an application where it is desired to maintain, for a long period of time, a performance (abrasion resistance) whereby water/oil repellency is less likely to be lowered even if rubbed repeatedly with a finger, and a performance (fingerprint stain removability) whereby a fingerprint adhered to a surface can be readily removed by wiping, for example, as a surface treatment agent for a member constituting the surface to be touched with a finger, of a touch panel.
In order to impart abrasion resistance to the surface layer formed on the surface of a substrate, for example, a hydrolyzable silyl group may be introduced at a terminal of the fluorinated ether compound, so that the fluorinated ether compound and the substrate will be chemically bonded. As a fluorinated ether compound for the purpose of forming a surface layer excellent in abrasion resistance, a fluorinated ether compound has been proposed wherein to each of both terminals of the fluorinated ether compound, three hydrolyzable silyl groups are introduced via a branched structure by pentaerythritol (Patent Document 1).